Well, I have to say that I like to play the games like solitaire and so on, and on 10 they have them on their own program. It has ads which doesn't disturb me that much but there is the option of payment in order to remove them.
Other than that, they did in fact offer it first, and now they are pushing it. It is not like they were pushing it from the very beginning. Plus they offer it free to those who had 7 or 8(.1) already. Others have to buy it. So what's the catch? You are not forced to pay anything for the upgrade because you are already their customer and this way they guarantee you will stay as their customer when they provide their new system for free. If you don't like it, why not change to Linux or Mac if you are so against the upgrade itself?